Grounding apparatus for electrographic copy apparatus

ABSTRACT

In electrographic apparatus employing a replaceable movable photoconductive member having a conductive layer, a photoconductive layer and an imbibed strip in the photoconductive layer connected to the conductive layer, a conductive rotatable member provides a continuous electrical path to a point of reference potential from the conductive layer through the imbibed conductive strip by having a line of contact with the top surface of the imbibed strip. The rotatable member is disposed so that its axis of rotation is skewed with respect to the velocity vector of such line of contact whereby a scrubbing force is imparted to the strip surface to clean it and thereby maintain a good electrical connection between the strip and the conductive rotatable member.

Unite States Patent [1 1 Edelman et al.

GROUNDING APPARATUS FOR ELECTROGRAPHIC COPY APPARATUS Assignee: Eastman Kodak Company,

Rochester, N.Y.

Filed: Sept. 5, 1972 Appl. No.: 285,963

U.S. Cl. 355/15, 339/9 RY, 355/16,

355/3 Int. Cl G03g 15/00 Field of Search 355/15, 3, l6;

339/5 R, 6, 9 R, 9 RY References Cited UNITED STATES PATENTS 4/1970 Caldwell et al. 355/3 Higgins et al. 339/9 RY July 3, 1973 [57] ABSTRACT In electrographic apparatus employing a replaceable movable photoconductive member having a conductive layer, a photoconductive layer and an imbibed strip in the photoconductive layer connected to the conductive layer, a conductive rotatable member provides a continuous electrical path to a point of reference potential from the conductive layer through the imbibed conductive strip by having a line of contact with the top surface of the imbibed strip. The rotatable member is disposed so that its axis of rotation is skewed with respect to the velocity vector of such line of contact whereby a scrubbing force is imparted to the strip surface to clean it and thereby maintain a good electrical connection between the strip and the conductive rotatable member.

2 Claims, 4 Drawing Figures BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrographic apparatus utilizing a photosensitive member having at least two layers, a conductive layer and a photoconductive layer. More particularly, the invention relates to apparatus for placing the conductive layer at a reference potenl0 tial.

2. Description of the Prior Art A number of electrophotographic processes and apparatus have been disclosed in which a photoconductive member is exposed through a transparent conductive layer; see, for example, U. S. Pat. No. 2,825,814 to Walkup; U. S. Pat. No. 2,986,535 to Gundlach; U. S. Pat. No. 2,676,100 to Huebner; U. S. Pat. No. 2,866,903 to Berchtold; U. 5. Pat. No. 3,256,089 to Clark et al.; and U. S. Pat. No. 2,277,013 to Carlson.

The effectiveness of these processes and apparatus is dependent upon the establishment of a point of reference potential, commonly ground, at one side of the conductive layer to facilitate the removal of charge from the photo-conductive layer at various processing stations along the path of movement of the photosensitive member. Prior apparatus have disclosed the use of mechanical contact in, for example, rolling (see U. S. Pat. No. 3,533,692 to Blanchette et al.) or wiping engagements (see U. S. Pat. No. 3,574,615 to Morse) with a conductive strip connected to the conductive layer to hold the conductive layer at a referenced potential. A difficulty with the prior approaches has been in establishing reliable electrical contact for in the usual electrophotographic process, toner and other particulate matter can be deposited on the surface of the strip thereby inadvertently varying the reference potential.

SUMMARY OF THE INVENTION It is an object of the invention to provide means for establishing reliable electrical contact between part of an electrographic apparatus and a conductive layer of a periodically replaceable photoconductive member used in said apparatus.

In accordance with the invention, it has been determined that if a rotatable member, preferably of cylindrical configuration providing a rolling line of contact engagement with the top surface of a conductive imbibed strip in a photosensitive web or member has its axis of rotation skewed with respect to the velocity vector of the strip at the line of contact, the top surface of the imbibed metalized strip is scrubbed clean thereby insuring good electrical contact.

Other objects of the invention and its various advantages will become apparent from the ensuing detailed description of the preferred embodiment shown below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic vertical section of an electrographic apparatus embodying the invention;

FIGS. 2A and 2B show various views of the rotatable member shown in FIG. 1 in contact with the top surface of an imbibed conductive strip of a photoconductive member; and

FIG. 3 is a cross-section taken along lines 3-3 of FIG. 2A.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a general understanding of an electrographic reproducing or copier apparatus wherein the invention has particular utility, reference is made to FIG. 1 wherein various stations of an electrophotographic apparatus are schematically illustrated. As in most elec' trophotographic copiers, an information medium 13 such as a document is illuminated by radiation from flash lamps 14. Such radiation is reflected from the medium and projected by a lens 15 onto a photoconductive member 16, shown as a web, to selectively dissipate change and form an electrostatic image. The photoconductive member 18 had previously been uniformly charged at a charging station 20.

The photoconductive member 16 as shown in FIG. 3 is a layered structure in the form of a sandwich having a support 40, for example, photographic film base, a conductive layer 42 formed on such base and a photoconductive layer 44 formed on the conductive layer 42 but less than coextensive therewith to uncover an area wherein there is disposed an imbibed conductive strip 46 which is connected to the conductive layer 42.

In accordance with general use in the art, the term conductive layer will be used to describe a thin layer of ordinarily conductive material, even though such layers are sometimes so thin that their surface resistivity is as high as 10' ohms per square inch or higher. It should be noted that some materials can be coated to a thickness which passes one-half the radiation striking it but which has a surface resistivity as low as 10 ohms per square inch. For a complete discussion of conductivity, transparency and thickness of such layers, reference is made to U. S. Pat. No. 3,245,833 to Trevoy.

The photoconductive layer 44 may comprise, for instance, a heterogeneous mixture of a bisphenol A- polycarbonate binder, a triarylmethane organic photoconductor and a pyrylium sensitizing dye.

The imbibed conductive strip 40 may be formed of a conductive lacquer which is imbibed through the uncovered area to bond to and make electrical contact with the conducting layer 42. Alternatively, the strip 46 may be formed of a metalized material.

Returning now to FIG. 1, apparatus 10 further includes a development station 22 at which the electrostatic image is contacted with finely divided charged toner particles that adhere to the photoconductive layer in a configuration defined by the electrostatic image; a transfer station 24 in which toner particles are transferred in the .image configuration to a receiving surface of a copy sheet 26 on which it can be subsequently permanently fused; and a cleaning station (not shown) in which residual toner is removed from the photoconductive layer so that it can be resused. In certain known modifications of this same system, one or more of these stations may be eliminated. For a more complete description of an electrographic apparatus, reference is made to commonly assigned copending patent application Ser. No. l9l,304 filed Sept. 21, l97l, entitled, CONTROL APPARATUS FOR ELECTRO- PI-IOTOGRAPHIC APPARATUS to Hickey et al. An example of an exemplary development station is set forth in U. S. Pat. No. 3,543,720 to Drexler.

To facilitate the selective discharge of the conducting layer 40, there is provided a reference potential or coupling means indicated generally at 50 which includes a rotatable conductive roller member 52.

In the disclosed embodiment, the term, reference potential" has been shown to be at ground level. However, it is to be understood that in certain applications within the scope of this invention, a reference potential other than ground may be desirable especially in the instance where it is desired to control the amount of charge deposited on the photoconductive layer 42.

Turning now to FIGS. 2A 2B, the conductive member 52 is preferably of cylindrical configuration but rollers having a circular cross-section such as cones, spheres and ellipsoids can also be utilized in accordance with the invention. The member 52 is rotatably mounted on bearings 54 which define the axis of rotation 53 of the member 52. A yoke member 56, formed of a highly conductive material is secured to the bearings. An electrical lead 60 is connected to the yoke and directly connected to ground potential. A spring assembly 66 is connected to the top surface of the yoke 52 and the main frame of the apparatus and urges the member 52 into a line of contact engagement with the top surface of the strip 46.

As shown most clearly in FIG. 2A, the yoke 56 holds the member 52 such that the axis of rotation 53 is skewed relative to the direction of movement of the line of contact portion of the strip 46. In operation as the web moves, the frictional engagement of the strip 26 and the member 52 causes the member 52 to rotate. Since the axis of rotation of the member 52 is skewed relative to the velocity vector of the top surface of the strip 46 at the line of contact, a lateral force of scrubbing action is applied to such surface to clean it of any particulate matter which may have been deposited thereon, thereby maintaining a good electrical contact. The scrubbing rate can be adjusted by adjusting the skewed position of the axis 53 and/or the force applied by the spring assembly 66.

The invention has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. For use in electrographic apparatus utilizing a movable photoconductive member having a photoconductive layer connected to a conductive layer, and a conductive strip connected to the conductive layer and defining an exposed surface, reference potential coupling means comprising:

a rotatable conductive member connected to a point of reference potential and disposed to have line of contact with the impact surface of the conductive strip which is skewed with respect to the velocity vector of the strip at such line of contact, whereby a scrubbing force is imparted to such surface to clean it.

2. In an electrographic apparatus having a movable, flexible photoconductive member formed of an electrically conducting layer formed on a support, a photoconductive layer formed on the conductive layer but which is less than coextensive with the electrically conductive layer to uncover an area of the electrically conductive layer and an imbibed conductive strip disposed in such uncovered area and connected to the conductive layer, the imbibed conductive strip defining a top surface means for establishing a connection between the top surface of the imbibed conductive strip to electrically connect the conducting layer to a reference potential comprising:

a. a conductive member having a rotatable cylindrical portion defining an axis of rotation;

b. means coupling said conductive member to a point of reference potential;

c. spring means coupled to said conductive member for urging said cylindrical portion into a line of contact with the top surface of the imbibed conductive strip; and

d. means coupled to said conductive'member and adapted to position such conductive member such that the axis of rotation of said cylindrical portion is skewed with respect to the velocity vector of the line of contact of the top surface of the strip to provide a scrubbing action to clean the top surface of such strip as said cylindrical portion rotates. 

2. In an electrographic apparatus having a movable, flexible photoconductive member formed of an electrically conducting layer formed on a support, a photoconductive layer formed on the conductive layer but which is less than coextensive with the electrically conductive layer to uncover an area of the electrically conductive layer and an imbibed conductive strip disposed in such uncovered area and connected to the conductive layer, the imbibed conductive strip defining a top surface means for establishing a connection between the top surface of the imbibed conductive strip to electrically connect the conducting layer to a reference potential comprising: a. a conductive member having a rotatable cylindrical portion defining an axis of rotation; b. means coupling said conductive member to a point of reference potential; c. spring means coupled to said conductive member for urging said cylindrical portion into a line of contact with the top surface of the imbibed conductive strip; and d. means coupled to said conductive member and adapted to position such conductive member such that the axis of rotation of said cylindrical portion is skewed with respect to the velocity vector of the line of contact of the top surface of the strip to provide a scrubbing action to clean the top surface of such strip as said cylindRical portion rotates. 